The rotary closed parallel cycle engine is similar to the previously disclosed series cycle rotary units with large loop transfer tubing between the hot and cold sides of each engine unit.
The previously described rotary closed series cycle engine system outlined in Disclosure Document No. 018274, contains a design inconsistancy of having the first unit to the last unit transfer tubing connection unequal to the normal diagonal tubing connections.
Although this design discrepancy can be satisfactorily resolved, it does entail some compromises and difficulty in arranging the long tubing runs in relation to the manifolds on both thermal sides of the rotary units.
The series gas flow arrangement and inconsistant tubing runs require that the tubing groups be made up and connected as one unit assembly, since they are not all identical and independent. The most serious deficiency in the series connection arrangement is that an internal gas leak occuring in any one of the rotary units will cause a loss of power in the engine system, due to the unit to unit gas flow.
The present parallel and independent transfer tubing arrangement avoids these problems, with all identical tubing runs and groups connected to the hot and cold manifolds of the same unit, directly across the axis of the engine system.
Each rotary (expander) unit operates in a similar way to a closed loop turbine (Brayton cycle), since the vanes are non-contacting with the cylinder walls, but unlike the turbine expander have a moderate compression ratio similar to that of the piston expander, (Stirling cycle).
An important factor in the effective operation of the rotary units is the critical application of ball bearings to each vane of each rotor so that the vanes are guided and controlled in their radial clearance with the cylinder bores. Friction and wear are thereby minimized and the rotary expander units operate at high efficiency.
The engine system will operate at high gas flow rates for a closed gas cycle because of the low friction expander and low internal gas flow resistance.
Hydrogen or helium gas will be the working medium for the engine system, which have been used successfully in Stirling piston engines recently. Hydrogen gas is advocated as a prime fuel source for the engine system due to its many advantages and availability.